Television receiver



April 1945. A. H. ROSENTHAL Re. 22,

TELEVISION RECEIVER Original Filed March 11, 1959 seamed Apr. 10, 1945 UNITED STATES PATENT OFFICE TELEVISION RECEIVER Adolph Henry Rosentlial, New York, N. Y., asslgnor, by mesne assignments, to Scophony Corporation of America, New York, N. Y., a corporation of Delaware "1 Claims. (01. 178-75) The present invention relates to television or like receivers, and is a continuation in part of my copending application Serial No. 253,182,

filed January 27, 1939, now Patent 2,330,171,

which is concerned with a novel image screen for such a receiver. By the term image screen is meant a screen, the optical properties of which change from point to point in accordance with received signals to be reproduced so that such a screen can be imaged with the aid of light from an external source on to a projection screen'to give a representation of the information reproduced in the image screen.

- If certain crystals, which are normally transparent to visible light, are struck by a beam of cathode rays, the electron charge thus injected into the crystal creates therein what will hereinafter and in the appended claims be referred to as opacity centers, and which can constitute an opaque deposit the degree of density of which depends on the intensity of.

the incident charge. Examples of such crystals are many of the alkali and alkaline earth halides, such as the chlorides, bromides and iodides of sodium and potassium, lithium bromide, calcium fluoride, and strontium fluoride and chloride; and also certain silver salts such as silver bromide. All these materials belong to the class of the so-called ionic crystals,"

1. e. crystals in which there are positive and negative components, and the forces that hold them together are electrostatic, at least in part. In'the case of the alkali halide crystals research has indicated that the opacity centers probably consist of neutral alkali atoms comprised of positive and negative charges which are loosely bound in the interior of the crystals in some of the deposit, may be for instance an increase of the deposit for lower intensities and a decrease of the deposit, whilst, over a range of higher intensities an increase in intensity will 'resul in a decrease of the deposit.

The materials exhibiting this property may be defined as those of the ionic type in which the injection of electrons into the crystal lattice can give rise to an opaque deposit in said lattice,

' constituted by opacity centers.

In my patent referred to above there is contemplated the use of a transparent crystalline material of the type defined in the image screen of a television or like receiver. The material may be in the form of a single flat crystal, :1 mosaic of small'crystals, or a micro-crystalline structure. A composite crystal (crystalline solid solution) or a mixtureof two'or more of such crystalline materials may be used.

In most cases. and particularly when the material is in the form of a'single crystal, a disappearance of the opaque deposit can be produced by maintaining the crystal in an electric field and at a suitable temperature, in which case the deposit is drawn through the crystal towards the positive pole producing the electric field. When it reaches the positive pole it disappears, leaving the crystal substantially transparent. The speed for the higher intensities, in a mannersimilar ,to the well known "Solarisation oi the latent photographic image. In this case, over a range of lower intensities of the incident radiation, increase in intensity will result in an increase of move'ment of the deposit depends upon the strength of the field and upon the temperature, and can be varied within wide limits by varying either magnitude. For a given field strength this speed of movement increases with the temperature of the crystal.

In the various embodiments described in my patent referred to above, conditions are such that the opaque deposit in the image screen constitutes in itself a visible image or reproduction of intelligence, and consequently this image can be directly projected on to a projection screen.

The formation of opacity centres in any given elemental area of the screen is accompanied by a corresponding change in the refractive index of this area, with respect to the refractive index of the remaining areas, due to the temporary liberation of electrons and the presence of free or loosely bound electrons in the substance of the screen. Instead of, or in addition to, the changes in opacity of the screen these changes in refractive index can be utilized to produce a visible image, and it is an object of the present invention to provide means whereby this utlilzation of the changes of refractive index can be achieved.

According to the present invention a television or the like receiver comprises a. screen of a ma teriai of the type defined, means for scanning thescreenwithacathoderaybeammodulated in intensity in accordance with the received signals to produce a change in the refractive index of the material of each elemental area 'in turn, the degree of change depending upon the instantaneous intensity of the beam striking the area, means for illuminating said screen, optical means for separating the portion of the light which undergoes a, change of direction due to said change in refractive index from the remaining portion, and means for directing one of said portions on to a projection screen.

The chief advantage of the present invention is that where the conditions are such that the density or tint of the opaque deposit-are not suitable for the production ofa satisfactory visible picture on the viewing screen, the method of the present invention can be used to overcome this diillculty,

The invention will now be described by way of example with reference to the accompanying drawing in which Fig. 1 shows schematically one form of theinvention, and

Fig. 2 shows an alternative form of construction of the image screen. Referring to Fig. 1, a cathode ray tube l is provided with a cathode 2, a control grid 3, a beam focussing coil 4, deflecting coils 5, 6 and an accelerating anode l; Pictureor other signals representative of intelligence intercepted by the receiver 8 are applied between the cathode and control grid in such a way that the positive potential of the grid decreases with increase in 1 signal strength, so that a modulated beam is produced and is swept over the image screen in .the usual manner. The image screen consists for instance of a flat crystal 9 of an alkali halide such as potassium chloride, provided on each side with an electrode III, I I designed to permit the passage or light. These electrodes are shown in the form direction, so that some of the light will pass the bar I. This light is utilized by the projection lens I! to form an image of the crystal on the projection screen l8.

In order to obtain a satisfactory picture on the projection screen it it is necessary that the quantity of light proceeding from .a given elemental area of the crystal which passes the bar It should be substantially proportional to the intensity of the radiant energy producing the change in the optical path in the elemental area, since it is this quantity of light which determines the intensity of the corresponding elemental area of the picture on the screen It. Now this quantity of light is not proportional to the optical path through the elemental area underconsideration but is proportional to the first diil'erential of this, i. e. if 1 represents the geometrical path throughthe crystal (if the light is incident normally on the crystal 1/ will represent the thickness of the crystal), if n represents the refractive index of the material of the elemental area, and if :1: represents any linear dimension of the area in-the plane of the crystal, then m gives the optical path and the quantity of light passing the bar It is proportional to A "screen may be produced by modulating the in- ,tensity of the scanning beam with high frequency oscillations derived from the source I8, the frequency of these oscillations being in the neighof thin transparent sputtered ,metallic layers,

but they can also be in the form of fine meshes or the like. The potential of the electrode II is maintained positive with respect to that of the electrode ill to provide an electric field in the crystal.

As explained'in detail in my patent referred to above a fugitive image in the form of opaque deposits is produced in the crystal 9 which travel through the crystal and disappear at the electrbde II, and normally it is possible to project this image directly on to a viewing screen. The formation of this image in the crystal screen is accompanied by a corresponding change in the refractive index of the crystal, this change, for any given elemental area of the crystal depending upon the intensity of the cathode ray beam when it strikes the area.

According to the present invention, this change in the refractive index is utilized informing a visible image on a viewing or projection screen.

In Fig. 1 the so-called Tiipler-Schlieren method is used for this purpose, andto this end the condenser lens system I! forms an image of the light source. I3 on the opaque bar 14, so that in the absence of any changes in the refractive index of the crystal 9, no light proceeding from the crystal can pass the .bar ll.

If now a change in the refractive index, and hence a change in the optical path through the material forming a given elemental area of the crystal is produced, the light rays passing through this area will experience, a change of bourhood of element frequency, so that there is vproduced a. gradient in the refractive index of the crystal in the line scanning direction over.

each elemental area, and hence a gradient in the tical path. This gradient is then altered by t e signal modulations superimposed on the high frequency modulations. This effect can also be produced byusing an unmodulated beam (except for the signal modulations) and interposing a line metallic grating (l9; Fig. 21) at or near the scanned surface of the crystal, or such a grating may be inthe form of a partly transparent metallic deposit on the crystal surface and acting at the same time as one of the crystal electrodes.

Alternative methods of producing the desired changes in refractive index in the image screen can be employed. These methods are substantially identical with the various alternative methods ,of producing the opaque deposit in the screen which are described in detail in my patent referred to above, and need not be described in the present specification.

I claim as my invention:

1. A receiver for electric signals representative of intelligence, such as television signals, including a cathode ray tube, a transparent screen in said tube substantially of ionic crystal material of the type in which the injection of electrons comprised by a beam developed in said tube can create opacity centers and a local change of its refractive index depending on the intensity of said beam, means for modulating the beam in accordance with signals to be reproduced and for causing it to scan said screen. a light source for causing light to pass through said screen, an optical stop on the. side of said screen remote from said light source, an optical system adapted i, eaiusmdaidmnw-i to form an image oi said light source on said 'stop. and optical means for utilizing light which by-passes said stop due to said effect of said scanning beam, to form an image of said tube screen on a projection screen.

2. A receiver for electric signals representative of intelligence. such as television signals, including a cathode ray tube, a transparent screen in said tube substantially of ionic crystal material of the type in which the injection of electrons comprised by a beam developed in said tube can give rise to opacity centers and to a local change of its refractive index depending on the intensity of said beam, a grating associated with said screen, means for modulating the intensity of said beam in accordance with signals to be reproduced and for causing it to scan said screen, a light source for causing light to pass through said screen, an optical stop on the side of said screen remote from said light source, an optical system adapted to form an image of said light source on said stop, and optical means for utilizing light which by-passes said stop due to the combined effects of said grating and scanning beam, to form an image of ,said tube screen on a projection screen.

3. A television or like receiver as claimed in claim 2 wherein said grating is in the form of a partly transparent metallic deposit on said 4. A receiver for electric signals representative oi intelligence, suchas television signals, includoscillations, means for modulating the intensity to of said beam in' accordance with said high frequency oscillations from said source and with signals to be reproduced, means for causing said beam to scan said screen, a light source for causing light to pass through said screen, an optical stop on the side of said screen remote from said light source, an optical system adapted to form an image of said light source on said stop, and optical means for utilizing light which by-p sses said stop due to said eifect of said modulated scanning beam, to form an image of said tube screen on a projection screen.

5. In a receiver for electric signals representative of intelligence, such as television signals, the

combination including a transparent screen substantially of ionic crystal material of the type in which the injection of electrons can create opacity centers and a local change or its refractive index depending on the intensity of the in Jected electron charge, means for developing a cathode ray beam and directing it upon elemental areas of said screen, a source of high frequency oscillations, means for modulating the intensity of said beam in accordance with received signals to be reproduced and with said oscillations, so that said beam produces in each impinged elemental screen area a gradient got the optical path therethrough the value of which depends on the combined modulation eifects of said oscillations said stop, and optical means forutilising light which by-passes said stop due to and in its quantity depending substantially on said gradient, to form an image of said tube screen on a projection screen.

6. A receiver for electric sign is representative of intelligence, such as television ignals, including in combination, a transparen screen substantially of ionic crystal material 0 the type in which the injection of electrons can create opacity centers and a local change of its refractive index depending on the intensity of the injected electron charge, means for developing a cathode ray beam and directing it upon elemental areas of J said screen, a source of high frequency oscillations, means for modulating said oscillations with received signals to be reproduced, means for modulating the intensity or said beam with said modulated oscillations so that said beam produces in each impinged elemental screen area a gradient in the optical path therethrough corresponding tosaid high frequency modulations and etered by said signal modulations, a light source for causing light to pass through said screen, an optical stop on the side of said screen remote from said light source, an optical system adapted to form an image of said light source on said stop,

. and optical means for utilising light which bypasses said stop due to and in its quantity substantially depending on said gradient, to form an image of said tube screen on a projection screen.

7. A receiver for electric signals representative of intelligence, such as television signals, including a cathode ray tube, a transparent screen in said tube substantially of ionic crystal material of the type in which the injection of electrons comprised by a beam developed in said tube can create opacity centers and a local change of its refractive index depending on the intensity of said beam, means for causing said beam to impinge elemental screen areas, a grating associated with said screen and arranged in the path of said beam for causing the latter to produce a gradient in the optical path through each impinged elemental screen area, means for modulating the intensity of said beam and thereby alter said gradient in accordance with signals to be reproduced, a light source for causing light to pass through said screen, an optical stop on the side of said screen remote from said light source, an optical .R'eissuo No. 22,628, 1 c April 1o, h

' ADoLPH- Rosana-HAL.

It is hereby cerfifiod 'jtheft "error -appemfira inthe'above nmhbe'r'od' 'fiatcn o requiring correction as' follows: In the drawing, Figure 2 ga shown below\ should be added as a Of the patent Q 4 page 2, second column, iinehS, for "Fig. 21" read "Fig.2"; apd that ,the said Letters Potent: should -boread with this correct-don thc roin that thosame may conform to the record of the case'in the'lP'aterit 03109.;

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